1. Field of the Invention
The present invention relates to a semiconductor device in which a semiconductor element is mounted on a mounting substrate by flip chip (face-down) bonding and a method for manufacturing the same.
2. Description of the Related Art
Conventionally, a flip chip bonding structure has been known as one method for mounting a semiconductor element on a mounting substrate.
In the conventional flip chip bonding structure as shown in FIG. 1A, a low-melting bump 3 such as solder is formed on each of electrodes 2 of a semiconductor element 1 by plating, or a ball bump such as gold and copper is formed thereon by ball bonding. A metal having a low melting point ("a low-melting metal") such as solder is applied to substrate electrodes 5 on a mounting substrate 4 by the plating, screen printing, or the like. The electrodes 2 and substrate electrodes 5 are aligned and bonded to each other by high-temperature reflow at a temperature exceeding the melting point of the low-melting metal.
In the conventional flip chip bonding structure, as illustrated in FIG. 1B, a misfit stress due to a difference in thermal expansion coefficient between the semiconductor element 1 and mounting substrate 4 is concentrated upon bump bonding portions 6. For this reason, a semiconductor device having such a structure has a drawback of being adversely influenced by a heat (temperature) cycle test or the like. In particular, if a resin type mounting substrate whose thermal expansion coefficient greatly differs from that of the semiconductor element is used, the reliability of bonding between them is considerably decreased.